Apparatus for measuring steering angle

ABSTRACT

An apparatus for measuring the steering angle of a wheel assembly including a suspended wheel mount and at least one suspension arm, the apparatus including a reference bracket, a rotating bracket and an angle sensor, the reference bracket and the rotating bracket each respectively including a measurement end and a mounting end, wherein the measurement ends of the reference and rotating brackets are rotatably coupled about a rotation coupling point such that the brackets can rotate with respect to one another, wherein the mounting end of the rotating bracket is coupled with the suspended wheel mount and the mounting end of the reference bracket is coupled with the suspension arm, and wherein the mounting end of the reference bracket is positioned on a plane defined by a steering axis of the suspended wheel mount and a rotation axis between the suspension arm and the suspended wheel mount.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a national stage entry of PCT/IL2022/050138 with an International Filing Date of Feb. 1, 2022, which claims the benefit of and priority to U.S. Provisional Application No. 63/143,982, filed Feb. 1, 2021, the contents of each of which are incorporated by reference herein their entirety.

FIELD OF THE DISCLOSED TECHNIQUE

The disclosed technique relates to a steering system in general, and to an apparatus for measuring a steering angle in particular.

BACKGROUND OF THE DISCLOSED TECHNIQUE

Measuring the steering angle in vehicles in general, and in autonomous vehicles in particular may provide information which can be employed for controlling the vehicle, for example, by providing feedback to a control system or alerting before steering lock occurs.

U.S. Pat. No. 6,568,696 to Osborn et al., entitled “Kingpin Angle Mounted Sensor” is directed to an angle sensor for sensing the angular position of a steerable wheel and hub relative to a longitudinal axis of a vehicle. The angle sensor is mounted in a bore in the kingpin. Thus, the angle sensor is made a part of the kingpin that supports the rotating wheel hub to its fixed wheel support housing on the axle of the vehicle.

U.S. Pat. No. 7,347,433 to Pressler et al., entitled “Wheel and Steering Sensor System” is directed to a steerable element angular sensor system. The sensor system includes a sensor shaft which includes a sensing axis. The sensing axis is positioned along an axis of rotation of a knuckle. A connector connects a yoke and the knuckle of the steering system. A sensor arm includes a first end attached to the sensor shaft and a second end for connecting to the knuckle traces movement of the knuckle about the axis of rotation of the knuckle. The sensor detects rotation of the knuckle and the connector.

U.S. Pat. No. 7,413,201 to Freytag et al., entitled “Steering System” is directed to a steering system with single-wheel suspensions, which are mounted on a respective wheel carrier. Each wheel carrier may be rotated about an axis of a rigidly connected swivel bolt. Each wheel carrier is further connected via a ball-and-socket joint on the swivel bolt, to a transverse steering element that is articulated to body of a vehicle. A steering angle sensor, including a rotatable input member, is located at an extension of the axis of the swivel bolt. The rotatable input member of the sensor is connected to the swivel bolt via an entrainment element that transmits the swivel motion of the bolt to detect the current swivel position of the wheel carrier.

SUMMARY OF THE PRESENT DISCLOSED TECHNIQUE

It is an object of the disclosed technique to provide a novel apparatus for measuring the steering angle of a wheel assembly including a suspended wheel mount and at least one suspension arm. According to an aspect of the disclosed technique, the apparatus includes a reference bracket, a rotating bracket and an angle sensor. The reference bracket includes a measurement end and a mounting end and the rotating bracket includes a measurement end and a reference end. The angle sensor is configured for measuring an angle between the reference bracket and the rotating bracket. The measurement end of the reference bracket and the measurement end of the rotating bracket are rotatably coupled about a rotation coupling point such that the reference bracket and the rotating bracket can rotate with respect to one another. The mounting end of the rotating bracket is coupled with the suspended wheel mount and the mounting end of the reference bracket is coupled with the suspension arm. The mounting end of the reference bracket is positioned on a plane defined by a steering axis of the suspended wheel mount and a rotation axis between the suspension arm and the suspended wheel mount during vertical motion of the suspended wheel mount. The vertical motion is relative to a reference frame.

According to another aspect of the disclosed technique, the apparatus includes a reference bracket, a rotating bracket and an angle sensor. The reference bracket includes a measurement end and a mounting end and the rotating bracket includes a measurement end and a reference end. The angle sensor is configured for measuring an angle between the reference bracket and the rotating bracket. The measurement end of the reference bracket and the measurement end of the rotating bracket are rotatably coupled about a rotation coupling point such that the reference bracket and the rotating bracket can rotate with respect to one another. The mounting end of the rotating bracket is coupled with the suspended wheel mount and the mounting end of the reference bracket is coupled with the suspension arm. The coupling of the mounting end of the reference bracket with the suspension arm is such that the reference bracket is at a fixed spatial relationship relative to an intersection point of a steering axis of the suspended wheel mount and a rotation axis between the suspension arm and the suspended wheel mount during vertical motion of the suspended wheel mount. The vertical motion is relative to a reference frame.

According to a further aspect of the disclosed technique, the apparatus includes a reference bracket, a rotating bracket and an angle sensor. The reference bracket includes a measurement end and a mounting end and the rotating bracket includes a measurement end and a reference end. The angle sensor is configured for measuring an angle between the reference bracket and the rotating bracket. The measurement end of the reference bracket and the measurement end of the rotating bracket are rotatably coupled about a rotation coupling point such that the reference bracket and the rotating bracket can rotate with respect to one another. The mounting end of the rotating bracket is coupled with the suspended wheel mount and the mounting end of the reference bracket is coupled with the suspension arm. The mounting end of the reference bracket is positioned on a plane defined by a line perpendicular to a steering axis of the suspended wheel mount and an intersection point of the steering axis with a rotation axis between the suspension arm and the suspended wheel mount during vertical motion of the suspended wheel mount. The vertical motion is relative to a reference frame.

According to another aspect of the disclosed technique, the apparatus includes a reference bracket, a rotating bracket and an angle sensor. The reference bracket includes a measurement end and a mounting end and the rotating bracket includes a measurement end and a reference end. The angle sensor is configured for measuring an angle between the reference bracket and the rotating bracket. The measurement end of the reference bracket and the measurement end of the rotating bracket are rotatably coupled about a rotation coupling point such that the reference bracket and the rotating bracket can rotate with respect to one another. The mounting end of the rotating bracket is coupled with the suspended wheel mount and the mounting end of the reference bracket is coupled with the suspension arm. The mounting end of the reference bracket is located on a rotation axis between the suspension arm and the suspended wheel mount. A longitudinal section of the reference bracket is parallel with a steering axis of the suspended wheel mount during vertical motion of the suspended wheel mount. The vertical motion is relative to a reference frame.

According to a further aspect of the disclosed technique, the measurement end of the reference bracket extends perpendicularly from a longitudinal section of the reference bracket. According to another aspect of the disclosed technique, a longitudinal section of the reference bracket is perpendicular with the steering axis. According to some aspects of the disclosed technique, the mounting end of the reference bracket is located on the rotation axis between the suspension arm and the suspended wheel mount. According to some aspects of the disclosed technique, the plane coincides with the suspension arm such that the rotation coupling point is located on the steering axis. According to some aspects of the disclosed technique, the plane is located on the rotation axis between the suspension arm and the suspended wheel mount.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosed technique will be understood and appreciated more fully from the following detailed description taken in conjunction with the drawings in which:

FIGS. 1A, 1B and 1C are schematic illustrations of a first wheel angle measurement apparatus for a wheel assembly constructed and operative in accordance with an embodiment of the disclosed technique;

FIGS. 2A, 2B and 2C are schematic illustrations of a second wheel angle measurement apparatus for a wheel assembly constructed and operative in accordance with another embodiment of the disclosed technique; and

FIG. 3 is a schematic illustration of a third wheel angle measurement apparatus for a wheel assembly constructed and operative in accordance with a further embodiment of the disclosed technique.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The disclosed technique overcomes the disadvantages of the prior art by providing an apparatus for measuring a steering angle of a suspended wheel relative to a reference frame in a wheel assembly, regardless of vertical motion of the wheel. Some wheel assemblies do not include a physical shaft at the steering axis that may hold the sensor for measuring a rotation of the suspended wheel mount with respect to the reference frame. When connecting a steering sensor between a steered suspended wheel mount and a stationary reference frame, the measured angle should not be affected by the vertical motion of the suspended wheel mount with respect to the reference frame.

The apparatus according to the disclosed technique includes a reference bracket, a rotating bracket and an angle sensor. A measurement end of the reference bracket is rotatably coupled with a measurement end of the rotating bracket such that the reference bracket and the rotating bracket can rotate with respect to one another about a rotating coupling point (also referred to as a rotation coupling point). The mounting end of the rotating bracket is coupled with the suspended wheel mount and the mounting end of the reference bracket is coupled with a suspension arm, such that the rotating coupling point is located on the steering axis, and the reference bracket and the rotating bracket rotate with respect to one another about the steering axis. Also, the reference bracket is coupled with the suspension arm such that the reference bracket is at a fixed spatial relationship relative to the intersection point of the steering axis and the rotation axis between the suspension arm and the suspended wheel mount, during a vertical motion of the suspended wheel mount. According to another alternative of the disclosed technique, the reference bracket is coupled with the suspension arm such that the mounting end of the suspension arm is located on the rotation axis between the suspension arm and the suspended wheel mount. According to a further alternative of the disclosed technique, a mounting end of the reference bracket is positioned on a plane defined by a line perpendicular to the steering axis and an intersection point of the steering axis and the rotation axis between the suspension arm and the suspended wheel mount, during a vertical motion of the suspended wheel mount relative to the reference frame. Thus, the rotation axis of the angle sensor remains aligned with the steering axis during vertical motion of the suspended wheel mount.

In the explanations which follow, the plane over which a vehicle maneuvers is referred to herein as a “horizontal plane” and an axis perpendicular to such a horizontal plane is referred to herein as a “vertical axis”. When the vehicle is a wheeled vehicle, the “horizontal plane” may be the plane (e.g., terrain) over which a wheel rolls. The terms “vertical motion” and “motion in the vertical direction” relate herein to motion along a vertical direction as per the above definition. Also, the term “in-motion direction” relates to the direction along which the wheel rolls (e.g., longitudinal direction of the vehicle). Typically, the in-motion axis is parallel (or substantially parallel, for example, when the wheel has a camber angle) to the horizontal plane. The term “lateral axis” relates to an axis perpendicular (or substantially perpendicular) to both the vertical axis and the in-motion axis, pointing in a direction perpendicular to the direction toward which the wheel rolls (i.e., lateral direction). Also, the terms “coupled at pivot point”, “pivotally coupled”, “coupled at rotation point” and “rotatably coupled” are all employed herein interchangeably and relate to two elements coupled such that these two elements may rotate with respect to one another. Furthermore, a reference frame herein relates, for example, to a chassis of a vehicle, or a frame of an assembly (e.g., a wheel assembly) attachable to a chassis of a vehicle.

Reference is now made to FIGS. 1A, 1B and 1C, which are schematic illustrations of a first wheel angle measurement apparatus, generally referenced 102, for a wheel assembly, generally referenced 100, constructed and operative in accordance with an embodiment of the disclosed technique. FIG. 1A is a front/rear view of wheel assembly 100, FIG. 1B is a top view of wheel assembly 100 and FIG. 1C is a side view of wheel assembly 100. Wheel assembly 100 is an exemplary wheel assembly employed herein for describing the operation of wheel angle measurement apparatus 102. Wheel assembly 100 includes a suspended wheel mount 104, two suspension arms, a first suspension arm 106 ₁ and a second suspension arm 106 ₂. Wheel assembly 100 may further include a spring-damper assembly 108. Wheel angle measurement apparatus 102 includes a reference bracket 110, a rotating bracket 112 and an angle sensor 114. Reference bracket 110 includes a measurement end 111 and a mounting end 113. Similarly, rotating bracket 112 includes a measurement end 115 and a mounting end 117.

One end of first suspension arm 106 ₁ is rotatably coupled with a reference frame 116 such that first suspension arm 106 ₁ and reference frame 116 are operable to rotate with respect to one another about an axis 119 ₁. Another end of first suspension arm 106 ₁ is rotatably coupled with suspended wheel mount 104 (e.g., via a ball joint) such that first suspension arm 106 ₁ and suspended wheel mount 104 are operable to rotate with respect to one another about an axis 121 ₁ and about a steering axis 122. Similarly, one end of second suspension arm 106 ₂ is rotatably coupled with a reference frame 116 such that second suspension arm 106 ₂ and reference frame 116 are operable to rotate with respect to one another about an axis 119 ₂, and another end of second suspension arm 106 ₂ is rotatably coupled (e.g., via a ball joint) with suspended wheel mount 104 such that second suspension arm 106 ₂ and suspended wheel mount 104 are operable to rotate with respect to one another about an axis 121 ₂ and about steering axis 122. Axes 119 ₁, 119 ₂, 121 ₁ and 121 ₂ are oriented such that suspended wheel mount 104 may move, relative to reference frame 116, in the vertical direction as indicated by an arrow 118.

In exemplary wheel assembly 100, one end of spring-damper assembly 108 is rotatably coupled with reference frame 116 such that spring-damper assembly 108 and reference frame 116 are operable to rotate with respect to one another. The other end of spring-damper assembly 108 is rotatably coupled with second suspension arm 106 ₂ such that spring-damper assembly 108 and second suspension arm 106 ₂ are operable to rotate with respect to one another.

Suspended wheel mount 104 is configured to be mounted with a wheel 120. Also, suspended wheel mount 104 is configured to rotate about a rotation axis (i.e., steering axis 122), for example, for steering purposes. According to the disclosed technique, wheel angle measurement apparatus 102 is configured to measure the rotation angle of suspended wheel mount 104 about axis 122. To that end, measurement end 111 of reference bracket 110 is rotatably coupled at a measurement end 115 of rotating bracket 112 such that reference bracket 110 and rotating bracket 112 can rotate with respect to one another about rotating coupling point 125. Mounting end 117 of rotating bracket 112 is coupled with suspended wheel mount 104. Mounting end 113 of reference bracket 110 is coupled with first suspension arm 106 ₁ such that rotating coupling point 125 with rotating bracket 112 is located on steering axis 122, and reference bracket 110 and rotating bracket 112 rotate with respect to one another about steering axis 122. Also, reference bracket 110 is coupled with suspension arm 106 ₁ such that reference bracket 110 (i.e., any selected point on reference bracket 110) is at a fixed spatial relationship relative to the intersection point of steering axis 122 and axis 121 ₁ during a vertical motion of suspended wheel mount 104 relative to reference frame 116. In the embodiment described herein in conjunction with FIGS. 1A-1C, measurement end 111 of reference bracket 110 perpendicularly extends from a longitudinal section of reference bracket 110. According to another alternative, reference bracket 110 is coupled with the suspension arm 106 ₁ such that mounting end 113 of reference bracket 110 is located on rotation axis 121 ₁ between the suspension arm and the suspended wheel mount and a longitudinal section of reference bracket 110 is parallel with steering axis 122 during a vertical motion of suspended wheel mount 104 relative to reference frame 116. According to yet another alternative, mounting end 113 of the reference bracket 110 is positioned on a plane defined by a line perpendicular (or substantially perpendicular) to steering axis 122 and the intersection point of steering axis 122 and axis 121 ₁ during a vertical motion of suspended wheel mount 104 relative to reference frame 116.

According to yet another alternative embodiment, mounting end 113 of reference bracket 110 is positioned on a plane defined by steering axis 122 and axis 121 ₁ during a vertical motion of suspended wheel mount 104 relative to reference frame 116. According to some embodiments, mounting end 113 is located on axis 121 ₁.

Angle sensor 114 is coupled with rotating bracket 112 and with reference bracket 110 at rotating coupling point 125. Thus, angle sensor 114 is configured for measuring the angle between reference bracket 110 and rotating bracket 112 and thus the angle between suspended wheel mount 104 (and thus wheel 120) and reference frame 116. Angle sensor 114 is, for example, a rotary potentiometer, a rotary magnetic hall-effect sensor or a rotary optical encoder.

As suspended wheel mount 104 rotates, rotating bracket 112 rotates therewith. Thus, rotating bracket 112 rotates relative to reference bracket 110 (i.e., since reference bracket is coupled with suspension arm 106 ₁ which does not rotate with suspended wheel mount 104). As suspended wheel mount 104 rotates, angle sensor 114 measures the relative angle between rotating bracket 112 and reference bracket 110. Thus, angle sensor 114 measures the rotation angle of suspended wheel mount about axis 122 (i.e., relative to reference frame 116), regardless of any vertical relative motion between suspended wheel mount 104 and reference frame 116. It is noted that suspension arm 106 ₁ is coupled with suspended wheel mount 104 such that the coupling point at axis 121 ₁ coincides with the kingpin of the suspended wheel mount. Thus according to the disclosed technique, angle sensor 114 can be prevented from experiencing any kind of analogous bump steer that may affect the steering angle measurement by angle sensor 114. The referred to analogous bump steer refers to any unintentional movement of reference bracket 110 with respect to rotating bracket 112 caused by the movement of mounting end 113 not remaining on an axis parallel to steering axis 122. The term “analogous” is used here as the referred to unintentional movement of reference bracket 110 is similar to the known concept of bump steer that happens in road vehicles when a suspended wheel mount unintentionally rotates/steers due to a bump in the road. Within the context of the disclosed technique, analogous bump steer refers to an unintentional movement of reference bracket 110 (and not to an unintentional movement of suspended wheel mount 104). According to the disclosed technique, suspension arm 106 ₁ is directly coupled with suspended wheel mount 104 and suspension arm 106 ₁ is also directly coupled with mounting end 113 of reference bracket 110. Due to the location of mounting end 113, any unintentional vertical movement of suspension arm 106 ₁ or unintentional horizontal movement of suspended wheel mount 104 will not cause any unintentional movement of reference bracket 110 with respect to rotating bracket 112, thereby avoiding analogous bump steer. As mentioned above, according to the disclosed technique, any unintentional movement between reference bracket 110 and rotating bracket 112, which is not due to actual steering (i.e., turning movement of suspended wheel mount 104), is substantially avoided as the motion of suspension arm 106 ₁ (shown by arrows 126A) is independent of the motion of suspended wheel mount 104 as it rotates around steering axis 122. The steering angle of suspended wheel mount 104 can thus be measured independent of the angle (not shown) of suspension arm 106 ₁ as it moves in the directions of arrows 126A.

Reference is now made to FIGS. 2A, 2B and 2C, which are schematic illustrations of a second wheel angle measurement apparatus, generally referenced 202, for a wheel assembly, generally referenced 200, constructed and operative in accordance with another embodiment of the disclosed technique. FIG. 2A is a side view of wheel assembly 200, FIG. 2B is an isometric view of wheel assembly 200 and FIG. 2C is a top view of wheel assembly 200 in a slightly steered position.

Wheel assembly 200 includes a suspended wheel mount 204 and two suspension arms, a first suspension arm 206 ₁ and a second suspension arm 206 ₂. Wheel angle measurement apparatus 202 includes a reference bracket 208, a rotating bracket 210 and an angle sensor 212. Reference bracket 208 includes a measurement end 216 and a mounting end 218. Similarly, rotating bracket 210 includes a measurement end 220 and a mounting end 222.

One end of first suspension arm 206 ₁ is rotatably coupled with a reference frame (e.g., similar to reference frame 104 in FIGS. 1A-1C yet not shown in FIGS. 2A-2C) such that first suspension arm 206 ₁ and the reference frame are operable to rotate with respect to one another. Another end of first suspension arm 206 ₁ is rotatably coupled with suspended wheel mount 204 such that first suspension arm 206 ₁ and suspended wheel mount 204 are operable to rotate with respect to one another about an axis 224 ₁. Similarly, one end of second suspension arm 206 ₂ is rotatably coupled with a reference frame such that second suspension arm 206 ₂ and the reference frame are operable to rotate with respect to one another about axis. Another end of second suspension arm 206 ₂ is rotatably coupled with suspended wheel mount 204 such that second suspension arm 206 ₂ and suspended wheel mount 204 are operable to rotate with respect to one another about an axis 224 ₂. Axes 224 ₁ and 224 ₂ are oriented such that suspended wheel mount 204 may move, relative to the reference frame, in the vertical direction as indicated by an arrow 226.

Suspended wheel mount 204 is configured to be mounted with a wheel (not shown). Also, suspended wheel mount 204 is configured to rotate about a rotation axis 228, for example, for steering purposes. According to the disclosed technique, wheel angle measurement apparatus 202 is configured to measure the rotation angle of suspended wheel mount 204 about axis 228. To that end, measurement end 216 of reference bracket 208 is rotatably coupled at a measurement end 220 of rotating bracket 210 such that reference bracket 208 and rotating bracket 210 can rotate with respect to one another about a rotating coupling point (not labeled). Mounting end 222 of rotating bracket 210 is coupled with suspended wheel mount 204. Mounting end 218 of reference bracket 208 is coupled with first suspension arm 206 ₁ such that the rotating coupling point with reference bracket 208 is located on steering axis 228, and reference bracket 208 and rotating bracket 210 rotate with respect to one another about steering axis 228. Also, reference bracket 208 is coupled with suspension arm 206 ₁ such that reference bracket 208 (i.e., any selected point on reference bracket 208) is at a fixed spatial relationship relative to the intersection point of steering axis 228 and axis 224 ₁ during a vertical motion of suspended wheel mount 204 relative to the reference frame. In FIGS. 2A, 2B and 2C, a positioning arm 230 couples reference bracket 208 with suspension arm 206 ₁ to maintain reference bracket 208 at a fixed spatial relationship relative to the intersection point of steering axis 228 and axis 224 ₁ during a vertical motion of suspended wheel mount 204 relative to the reference frame and to maintain the rotating coupling point with rotating bracket 210 on steering axis 228. It is noted that the only point of contact between reference bracket 208 and suspension arm 206 ₁ is where positioning arm 230 couples reference bracket 208 with suspension arm 206 ₁. Thus reference bracket 208 can be prevented from any kind of analogous bump steer from unintentional movements of suspension arm 206 ₁ and/or suspended wheel mount 204, which would affect the measurements of angle sensor 212. Analogous bump steer in this respect refers to any sideways motion of reference bracket 208 caused by vertical motion of suspension arm 206 ₁. According to the disclosed technique, by coupling suspension arm 206 ₁ with reference bracket 208 indirectly via positioning arm 230, analogous bump steer of reference bracket 208 can be avoided.

According to another alternative, positioning arm 230 couples reference bracket 208 with suspension arm 206 ₁ such that mounting end 218 of reference bracket 208 is located on rotation axis 224 ₁ between suspension arm 206 ₁ and suspended wheel mount 204. According to yet another alternative, mounting end 218 of reference bracket 208 is positioned on a plane defined by a line perpendicular to steering axis 228 and the intersection point of steering axis 228 and rotation axis 224 ₁, during a vertical motion of suspended wheel mount 204 relative to the reference frame. Thus, the rotation axis of angle sensor 212 remains aligned with steering axis 228, during vertical motion of suspended wheel mount 204. In the embodiment described herein in conjunction with FIGS. 2A-2C, measurement end 216 of reference bracket 208 perpendicularly extends from a longitudinal section of reference bracket 208.

In general, a positioning arm, such as positioning arm 230 may be employed in cases where the reference bracket cannot be coupled with the suspension arm as described above, for example, due to the shape of the suspension arm, or other structural limitations. The positioning arm may be an integral part of the suspension arm or attached thereto, for example, by bolts.

Angle sensor 212 is coupled with rotating bracket 210 and with reference bracket 208 at the rotating coupling point. Thus, angle sensor 212 is configured for measuring the angle between reference bracket 208 and rotating bracket 210 and thus the angle between suspended wheel mount 204 and the reference frame. Similar to angle sensor 114 (FIGS. 1A-1C), angle sensor 212 is, for example, a rotary potentiometer, a rotary magnetic hall-effect sensor or a rotary optical encoder.

As suspended wheel mount 204 rotates, rotating bracket 210 rotates therewith. Thus, rotating bracket 210 rotates relative to reference bracket 208 (i.e., since reference bracket 208 is coupled with suspension arm 206 ₁ which does not rotate with suspended wheel mount 204). As suspended wheel mount 204 rotates, angle sensor 212 measures the relative angle between rotating bracket 210 and reference bracket 208. Thus, angle sensor 212 measures the rotation angle of suspended wheel mount 204 about axis 228, regardless of any vertical relative motion between suspended wheel mount 204 and the reference frame. Thus, as mentioned above, any issues related to analogous bump steer of the reference bracket (which could affect the measurement of the angle sensor) can be avoided between the reference frame and suspended wheel mount 204.

In the examples brought forth above in conjunction with FIGS. 1A-1C and 2A-2C, the wheel angle measurement apparatus is attached to the upper side of the wheel assembly. However, the wheel angle measurement apparatus of the disclosed technique may also be attached to the bottom side of the wheel assembly. Reference is now made to FIG. 3 , which is a schematic illustration of a third wheel angle measurement apparatus, generally referenced 302, for a wheel assembly, generally referenced 300, constructed and operative in accordance with a further embodiment of the disclosed technique. Wheel assembly 300 includes a suspended wheel mount 304, two suspension arms, a first suspension arm 306 ₁ and a second suspension arm 306 ₂ and a spring-damper assembly 308. Wheel angle measurement apparatus 302 includes a reference bracket 310, a rotating bracket 312 and an angle sensor 314. Reference bracket 310 includes a measurement end 311 and a mounting end 313. Similarly, rotating bracket 312 includes a measurement end 315 and a mounting end 317.

One end of first suspension arm 306 ₁ is rotatably coupled with a reference frame 316 such that first suspension arm 306 ₁ and reference frame 316 are operable to rotate with respect to one another about an axis 319 ₁. Another end of first suspension arm 306 ₁ is rotatably coupled with suspended wheel mount 304 (e.g., via a ball joint) such that first suspension arm 306 ₁ and suspended wheel mount 304 are operable to rotate with respect to one another about an axis 321 ₁. Similarly, one end of second suspension arm 306 ₂ is rotatably coupled with reference frame 316 such that second suspension arm 306 ₂ and reference frame 316 are operable to rotate with respect to one another about an axis 319 ₂, and another end of second suspension arm 306 ₂ is rotatably coupled (e.g., via a ball joint) with suspended wheel mount 304 such that second suspension arm 306 ₂ and suspended wheel mount 304 are operable to rotate with respect to one another about an axis 321 ₂. Axes 319 ₁, 319 ₂, 321 ₁ and 321 ₂ are oriented such that suspended wheel mount 304 may move, relative to reference frame 316, in the vertical direction as indicated by an arrow 318.

In exemplary wheel assembly 300, one end of spring-damper assembly 308 is rotatably coupled with reference frame 316 such that spring-damper assembly 308 and reference frame 316 are operable to rotate with respect to one another. The other end of spring-damper assembly 308 is rotatably coupled with second suspension arm 306 ₂ such that spring-damper assembly 308 and second suspension arm 306 ₂ are operable to rotate with respect to one another.

Suspended wheel mount 304 is configured to be mounted with a wheel 320. Also, suspended wheel mount 304 is configured to rotate about a rotation axis 322, for example, for steering purposes. According to the disclosed technique, wheel angle measurement apparatus 302 is configured to measure the rotation angle of suspended wheel mount 304 about axis 322. To that end, measurement end 311 of reference bracket 310 is rotatably coupled at a measurement end 315 of rotating bracket 312 such that reference bracket 310 and rotating bracket 312 can rotate with respect to one another about a rotating coupling point. Mounting end 317 of rotating bracket 312 is coupled with suspended wheel mount 304. Mounting end 313 of reference bracket 310 is coupled with second suspension arm 306 ₂ such that the rotating coupling point with rotating bracket 312 is located on steering axis 322, and reference bracket 310 and rotating bracket 312 rotate with respect to one another about steering axis 322. Also, reference bracket 310 is coupled with suspension arm 306 ₂ such that reference bracket 310 (i.e., any selected point on reference bracket 310) is at a fixed spatial relationship relative to the intersection point of steering axis 322 and axis 321 ₂ during a vertical motion of suspended wheel mount 304 relative to reference frame 316. According to another alternative, mounting end 313 of reference bracket 310 is coupled with suspension arm 306 ₂ such that mounting end 313 of reference bracket 310 is located on rotation axis 321 ₂ between suspension arm 306 ₂ and suspended wheel mount 304. According to yet another alternative, mounting end 313 of reference bracket 310 is positioned on a plane defined by a line perpendicular to steering axis 322 and the intersection point of steering axis 322 and rotation axis 321 ₂, during a vertical motion of suspended wheel mount 304 relative to reference frame 316. Thus, the rotation axis of angle sensor 314 remains aligned with steering axis 322 during vertical motion of suspended wheel mount 304.

Angle sensor 314 is coupled with rotating bracket 312 and with reference bracket 310 at the rotating coupling point. Thus, angle sensor 314 is configured for measuring the angle between reference bracket 310 and rotating bracket 312 and thus the angle between wheel 320 and reference frame 316. Angle sensor 314 is, for example, a rotary potentiometer, a rotary magnetic hall-effect sensor or a rotary optical encoder.

As suspended wheel mount 304 rotates, rotating bracket 312 rotates therewith. Thus, rotating bracket 312 rotates relative to reference bracket 310 (i.e., since reference bracket 310 is coupled with suspension arm 306 ₂ which does not rotate with suspended wheel mount 304). As suspended wheel mount 304 rotates, angle sensor 314 measures the relative angle between rotating bracket 312 and reference bracket 310. Thus, angle sensor 314 measures the rotation angle of suspended wheel mount 304 about axis 322 (i.e., relative to reference frame 316), regardless of any relative vertical motion between suspended wheel mount 304 and reference frame 316. As mentioned above, reference bracket 310 is directly coupled with second suspension arm 306 ₂ with the location of mounting end 313 preventing any analogous bump steer of reference bracket 310 via unintentional movements of second suspension arm 306 ₂.

As described above in conjunction with FIGS. 1A-1C, 2A-2C and 3 , the wheel angle measurement apparatus according to the disclosed technique is positioned outside the volume defined by the wheel assembly. This enables adding mechanical and/or electrical sub-systems within this volume. Also, positioning the wheel angle measurement apparatus according to the disclosed technique outside the volume defined by the wheel assembly does not limit the range of motion (i.e., vertical motion or rotational motion) of the suspended wheel mount, and thus of the wheel, relative to the reference frame. It is also noted that a wheel angle measurement apparatus according to the disclosed technique is not directly connected to the steering joints.

Furthermore, an angle measurement apparatus according to the disclosed technique, as described above in conjunction with FIGS. 1A-1C, 2A-2C and 3 , maintains the rotation axis of the angle sensor aligned with the steering axis, during the vertical motion of the suspended wheel mount. Thus, employing an angle measurement apparatus according to the disclosed technique, reduces measurements errors resulting from rotation of the angle sensor during vertical motion of the wheel (i.e., even if the angle of the wheel, relative to the reference frame, did not change). As mentioned above, the disclosed technique also prevents any issues related to analogous bump steer of the reference bracket (which would affect the measurement of the angle sensor). In addition, the disclosed technique in FIGS. 1A-1C, 2A-2C and 3 has been shown and described as a reference frame coupled with a suspended wheel mount via two suspension arms, however the disclosed technique can be used in wheel assemblies where the reference frame is coupled with the suspended wheel mount via at least one suspension arm, as well as via a plurality of suspension arms. Thus the disclosed technique is not limited to two suspension arms as shown in the figures.

It will be appreciated by persons skilled in the art that the disclosed technique is not limited to what has been particularly shown and described hereinabove. Rather the scope of the disclosed technique is defined only by the claims, which follow. 

The invention claimed is:
 1. An apparatus for measuring the steering angle of a wheel assembly comprising a suspended wheel mount and at least one suspension arm, the apparatus comprising: a reference bracket comprising a measurement end and a mounting end; a rotating bracket comprising a measurement end and a mounting end; and an angle sensor, configured for measuring an angle between said reference bracket and said rotating bracket about a rotation axis of said angle sensor, wherein said measurement end of said reference bracket and said measurement end of said rotating bracket are rotatably coupled about a rotation coupling point such that said reference bracket and said rotating bracket can rotate with respect to one another; wherein said mounting end of said rotating bracket is coupled with said suspended wheel mount and said mounting end of said reference bracket is coupled with said at least one suspension arm; and wherein said mounting end of said reference bracket is positioned on a plane defined by a steering axis of said suspended wheel mount and a rotation axis between said at least one suspension arm and said suspended wheel mount during vertical motion of said suspended wheel mount, said vertical motion being relative to a reference frame, thereby keeping said rotation axis of said angle sensor aligned with said steering axis during vertical motion of said suspended wheel mount.
 2. The apparatus according to claim 1, wherein said measurement end of said reference bracket extends perpendicularly from a longitudinal section of said reference bracket.
 3. The apparatus according to claim 1, wherein a longitudinal section of said reference bracket is perpendicular with said steering axis.
 4. The apparatus according to claim 1, wherein said mounting end of said reference bracket is located on said rotation axis between said at least one suspension arm and said suspended wheel mount.
 5. The apparatus according to claim 1, wherein said plane coincides with said at least one suspension arm such that said rotation coupling point is located on said steering axis.
 6. The apparatus according to claim 1, wherein said plane is located on said rotation axis between said at least one suspension arm and said suspended wheel mount.
 7. The apparatus according to claim 1, wherein said apparatus is coupled with an upper end of said suspended wheel mount.
 8. The apparatus according to claim 1, wherein said apparatus is coupled with a lower end of said suspended wheel mount.
 9. The apparatus according to claim 1, wherein said angle sensor is coupled with said rotating bracket at said rotation coupling point.
 10. The apparatus according to claim 1, wherein said angle sensor is coupled with said reference bracket at said rotation coupling point.
 11. An apparatus for measuring the steering angle of a wheel assembly comprising a suspended wheel mount and at least one suspension arm, the apparatus comprising: a reference bracket comprising a measurement end and a mounting end; a rotating bracket comprising a measurement end and a mounting end; and an angle sensor, configured for measuring an angle between said reference bracket and said rotating bracket about a rotation axis of said angle sensor, wherein said measurement end of said reference bracket and said measurement end of said rotating bracket are rotatably coupled about a rotation coupling point such that said reference bracket and said rotating bracket can rotate with respect to one another; wherein said mounting end of said rotating bracket is coupled with said suspended wheel mount and said mounting end of said reference bracket is coupled with said at least one suspension arm; and wherein said coupling of said mounting end of said reference bracket with said at least one suspension arm is such that said reference bracket is at a fixed spatial relationship relative to an intersection point of a steering axis of said suspended wheel mount and a rotation axis between said at least one suspension arm and said suspended wheel mount during vertical motion of said suspended wheel mount, said vertical motion being relative to a reference frame, thereby keeping said rotation axis of said angle sensor aligned with said steering axis during vertical motion of said suspended wheel mount.
 12. The apparatus according to claim 11, wherein said measurement end of said reference bracket extends perpendicularly from a longitudinal section of said reference bracket.
 13. The apparatus according to claim 11, wherein a longitudinal section of said reference bracket is perpendicular with said steering axis.
 14. The apparatus according to claim 11, wherein said apparatus is coupled with an upper end of said suspended wheel mount.
 15. The apparatus according to claim 11, wherein said apparatus is coupled with a lower end of said suspended wheel mount.
 16. The apparatus according to claim 11, wherein said angle sensor is coupled with said rotating bracket at said rotation coupling point.
 17. The apparatus according to claim 11, wherein said angle sensor is coupled with said reference bracket at said rotation coupling point.
 18. An apparatus for measuring the steering angle of a wheel assembly comprising a suspended wheel mount and at least one suspension arm, the apparatus comprising: a reference bracket comprising a measurement end and a mounting end; a rotating bracket comprising a measurement end and a mounting end; and an angle sensor, configured for measuring an angle between said reference bracket and said rotating bracket about a rotation axis of said angle sensor, wherein said measurement end of said reference bracket and said measurement end of said rotating bracket are rotatably coupled about a rotation coupling point such that said reference bracket and said rotating bracket can rotate with respect to one another; wherein said mounting end of said rotating bracket is coupled with said suspended wheel mount and said mounting end of said reference bracket is coupled with said at least one suspension arm; and wherein said mounting end of said reference bracket is positioned on a plane defined by a line perpendicular to a steering axis of said suspended wheel mount and an intersection point of said steering axis with a rotation axis between said at least one suspension arm and said suspended wheel mount during vertical motion of said suspended wheel mount, said vertical motion being relative to a reference frame, thereby keeping said rotation axis of said angle sensor aligned with said steering axis during vertical motion of said suspended wheel mount.
 19. The apparatus according to claim 18, wherein said measurement end of said reference bracket extends perpendicularly from a longitudinal section of said reference bracket.
 20. The apparatus according to claim 18, wherein a longitudinal section of said reference bracket is perpendicular with said steering axis.
 21. The apparatus according to claim 18, wherein said plane coincides with said at least one suspension arm such that said rotation coupling point is located on said steering axis.
 22. The apparatus according to claim 18, wherein said plane is located on said rotation axis between said at least one suspension arm and said suspended wheel mount.
 23. The apparatus according to claim 18, wherein said apparatus is coupled with an upper end of said suspended wheel mount.
 24. The apparatus according to claim 18, wherein said apparatus is coupled with a lower end of said suspended wheel mount.
 25. The apparatus according to claim 18, wherein said angle sensor is coupled with said rotating bracket at said rotation coupling point.
 26. The apparatus according to claim 18, wherein said angle sensor is coupled with said reference bracket at said rotation coupling point.
 27. An apparatus for measuring the steering angle of a wheel assembly comprising a suspended wheel mount and at least one suspension arm, the apparatus comprising: a reference bracket comprising a measurement end and a mounting end; a rotating bracket comprising a measurement end and a mounting end; and an angle sensor, configured for measuring an angle between said reference bracket and said rotating bracket about a rotation axis of said angle sensor, wherein said measurement end of said reference bracket and said measurement end of said rotating bracket are rotatably coupled about a rotation coupling point such that said reference bracket and said rotating bracket can rotate with respect to one another; wherein said mounting end of said rotating bracket is coupled with said suspended wheel mount and said mounting end of said reference bracket is coupled with said at least one suspension arm; wherein said mounting end of said reference bracket is located on a rotation axis between said at least one suspension arm and said suspended wheel mount; and wherein a longitudinal section of said reference bracket is parallel with a steering axis of said suspended wheel mount, during vertical motion of said suspended wheel mount, said vertical motion being relative to a reference frame, thereby keeping said rotation axis of said angle sensor aligned with said steering axis during vertical motion of said suspended wheel mount.
 28. The apparatus according to claim 27, wherein said measurement end of said reference bracket extends perpendicularly from a longitudinal section of said reference bracket.
 29. The apparatus according to claim 27, wherein a longitudinal section of said reference bracket is perpendicular with said steering axis.
 30. The apparatus according to claim 27, wherein said apparatus is coupled with an upper end of said suspended wheel mount.
 31. The apparatus according to claim 27, wherein said apparatus is coupled with a lower end of said suspended wheel mount.
 32. The apparatus according to claim 27, wherein said angle sensor is coupled with said rotating bracket at said rotation coupling point.
 33. The apparatus according to claim 27, wherein said angle sensor is coupled with said reference bracket at said rotation coupling point. 